|PIC1|Boris Johnson and Ken Livingstone traded personal attacks on Wednesday as they made a final push for votes on the last day of campaigning in the London mayoral race.

The Conservative hopeful sent half a million emails to Londoners accusing Livingstone of being "tired, out-of-date and beset by allegations of sleaze".

The Labour mayor posted a million postcards with the message "Don't Vote for a Joke" and predicted voters would decide at the last minute that they couldn't risk electing Johnson.

The campaign has grown increasingly bitter in the run-up to polling day on Thursday. The main candidates have clashed over crime, the congestion charge and public transport.

The winner will oversee the biggest investment in transport infrastructure in decades and will help prepare the capital for the Olympic Games in 2012.

Most polls put Johnson ahead, although Livingstone's camp hotly contests the way they were conducted.

"The election is not a joke, it will affect the day to day life of every Londoner," Livingstone's campaign team said. "The momentum has moved decisively in Ken's direction."

In an interview, the mayor predicted that his rival would suffer from "hovering pencil syndrome", where voters decide at the last moment not to take a risk on a change at City Hall.

"Although people may be toying with the idea of voting for Boris, when it comes to it they will find they just can't do it," he told Wednesday's Evening Standard newspaper.

Livingstone's camp has repeatedly accused Johnson of not being a serious candidate.

They have played on his popular image as a floppy-haired joker best known by many as the sometime host of "Have I Got News for You" and as a former newspaper columnist responsible for a string of gaffes.

Johnson has hit back by accusing Livingstone of cronyism and a lack of fresh ideas after eight years in office. The mayor's advisor Lee Jasper resigned in March over allegations of misuse of public funds.

In a statement, Johnson said: "Tomorrow you have a choice: between new policies and fresh energy from a new mayor in City Hall, or more of the same from a tired, out-of-date administration that is beset by allegations of sleaze."

Liberal Democrat Brian Paddick appealed to undecided voters to ignore the top two candidates and vote for him.

"I am fed up with career politicians and their broken promises - and even if asked, I will not work for either Ken Livingstone or Boris Johnson," he said.

Polling stations open between 7 a.m. and 10 p.m. on Thursday, counting begins at 9 a.m. on Friday and the result will be announced about 12 hours later.